Impulse combustion cleaning system and method

ABSTRACT

A system for removing accumulated debris from a surface of a vessel. The system comprises a vessel having a surface to be cleaned. A impulse cleaning device defines a combustion chamber in which combustible fuel and air are mixed and ignited to produce supersonic combustion that is directed at the surface to be cleaned within the vessel. A sensor is associated with the impulse cleaning device. The sensor is for detecting a condition within the impulse cleaning device and generating a signal in response to a detected condition.

BACKGROUND

The invention relates generally to an impulse combustion cleaning system. More specifically, the invention relates to sensing a condition in the impulse combustion cleaning system.

Industrial boilers operate by using a heat source to create steam from water or another working fluid, which can then be used to drive a turbine in order to supply power. The heat source may be a combustor that burns a fuel in order to generate heat, which is then transferred into the working fluid via a heat exchanger. Burning the fuel may generate residues that can be left behind on the surface of the combustor or heat exchanger. Such buildups of soot, ash, slag, or dust on heat exchanger surfaces can inhibit the transfer of heat and therefore decrease the efficiency of the system. Periodic removal of such built-up deposits maintains the efficiency of such boiler systems.

Pressurized steam, water jets, acoustic waves, and mechanical hammering have been used to remove built-up deposits. These systems can be costly to maintain and the effectiveness of these systems varies.

A supersonic combustion or impulse cleaning system has recently been used in an attempt to remove built-up deposits. Supersonic combustion events create strong impulse waves that remove the built-up deposits and accumulated debris from the heat exchanger surfaces. Typically, the impulse cleaning system would need to be located in an area either visually or audibly accessible by an operator or attendant in order to verify operation of the device. Sensors, such as pressure or temperature probes, can be used but these must be located such that the sensors are exposed to hot and sometimes caustic gases of the combustion process. This exposure can decrease the service life of the sensors.

Therefore, there is a need for development of effective and reliable impulse cleaning systems.

BRIEF DESCRIPTION

An effective and reliable impulse cleaning system for removing built-up deposits and accumulated debris from a surface within a vessel is provided, according to one aspect of the invention. The system includes a vessel having a surface to be cleaned. The system also includes an impulse cleaning device that defines a combustion chamber in which combustible fuel and air are mixed and ignited to produce supersonic combustion that is directed at the surface to be cleaned within the vessel. A sensor is associated with the impulse cleaning device. The sensor is for detecting a condition within the impulse cleaning device and generating a signal in response to a detected condition.

According to another aspect of the invention a cleaner for removing built-up deposits and accumulated debris from a surface of a vessel is provided. The cleaner includes an impulse cleaning device defining a combustion chamber in which combustible fuel and air are mixed. The fuel and air mixture is ignited to produce supersonic combustion that is directed at a surface to be cleaned within the vessel. A sensor is operably connected with the impulse cleaning device. The sensor detects a condition within the impulse cleaning device and generates a signal in response to a detected condition.

According to yet another aspect of the invention a method for removing built-up deposits and accumulated debris from a surface within a vessel is provided. The method comprises the steps of providing an impulse cleaning device defining a combustion chamber. A flow of air is delivered into the combustion chamber. A flow of combustible fuel is delivered into the flow of air in the combustion chamber. The combustible fuel and air are mixed within the combustion chamber. The fuel and air mixture is periodically ignited to produce supersonic combustion. The supersonic combustion is directed into the vessel at a surface to be cleaned to loosen and remove accumulated debris from the surface of the vessel. The supersonic combustion in the impulse cleaning device is sensed and a signal is generated in response to detecting the supersonic combustion.

DRAWINGS

These and other features, aspects, and advantages of the invention will be better understood when the following detailed description is read with reference to the accompanying drawing, in which:

FIG. 1 is a schematic representation of an impulse cleaning system according to one aspect of the invention;

FIG. 2 is an enlarged schematic representation of a portion of the impulse cleaning system illustrated in FIG. 1;

FIG. 3 is a schematic representation of an impulse cleaning system according to another aspect of the invention; and

FIG. 4 is an enlarged schematic representation of a portion of the impulse cleaning system illustrated in FIG. 3.

DETAILED DESCRIPTION

Soot or other buildup on heat exchanger surfaces in industrial boilers can cause losses in the overall efficiency of the boiler due to a reduction in the amount of heat that is actually transferred into a working fluid. This is often reflected by an increase in the exhaust gas temperature from the process, as well as an increase in the fuel-burn rate required to maintain steam production and a given energy output. Traditionally, the complete removal of buildup from the heat exchanger surfaces requires the boiler to be shut down while a cleaning process is performed. Online cleaning techniques generally have high maintenance costs or incomplete cleaning results.

In one aspect of the invention, an impulse cleaning system located external to the boiler is used to generate a series of detonations or quasi-detonations that are directed into a fouled portion of the boiler. The resulting impulse waves impact boiler surfaces and loosen buildup from the surfaces. The loosened debris is free to fall to the bottom of the boiler and then may exit the boiler through hoppers. As will be discussed below, the use of repeated impulses has advantages over traditional cleaning techniques, such as steam blowers or purely acoustic soot removal devices.

It is also desirable that a cleaning system for a boiler be able to operate to quickly remove buildups in order to minimize the downtime for the boiler. It is also desirable that the installation of such cleaner be reliably monitored to assure that it is functioning and functioning at a high level of performance. An impulse based cleaning system that can provide these and other features will be described in more detail below.

As used herein, the term “impulse cleaning system” will refer to a device or system that produces both a pressure rise and velocity increase from the detonation or quasi-detonation of a fuel and oxidizer. The impulse cleaning system can be operated in a repeating mode to produce multiple detonations or quasi-detonations within the device. These detonations or quasi-detonations form a pulse of energy in the form of a shock wave that can be used for cleaning built-up deposits and accumulated debris from surfaces of a boiler vessel. A “detonation” is a supersonic combustion event in which a shock wave is coupled to a combustion zone. The shock wave is sustained by the energy release from the combustion zone, resulting in combustion products at a higher pressure than the combustion reactants. For simplicity, the term “detonation” as used herein will be meant to include both detonations and quasi-detonations. A “quasi-detonation” is a supersonic turbulent combustion process that produces a pressure rise and velocity increase higher than a pressure rise and velocity increase produced by a sub-sonic deflagration wave.

Exemplary impulse cleaning systems, some of which will be discussed in further detail below, include an ignition device for igniting a fuel/oxidizer mixture, and a detonation chamber or zone in which pressure wave fronts initiated by the combustion coalesce to produce a detonation wave. Each detonation or quasi-detonation is initiated either by an external ignition source, such as a spark discharge, laser pulse, heat source, or plasma igniter, or by gas dynamic processes such as shock focusing, auto ignition or an existing detonation wave from another source (cross-fire ignition). The detonation chamber geometry allows the pressure increase behind the detonation wave to drive the detonation wave and also to blow the combustion products out of the impulse cleaning system.

Various chamber geometries can support detonation formation, including round chambers, tubes, resonating cavities and annular chambers. Such chambers may be of constant or varying cross-section, both in area and shape. Exemplary chambers include cylindrical tubes and tubes having polygonal cross-sections, such as, for example, hexagonal tubes or including obstacles to promote detonation, such as disclosed in U.S. patent application Ser. No. 11/669,582 filed Jan. 31, 2007. As used herein, “downstream” refers to a direction of flow of at least one of fuel or oxidizer.

One embodiment of an exemplary impulse cleaning device 20 suitable for use with an industrial boiler is illustrated schematically in FIG. 1. The impulse cleaning system 20, according to one aspect of the invention, includes an impulse cleaning device 22, a sensor 24 associated with the impulse cleaning device and a monitor/controller 26. The impulse cleaning system 20 is constructed and mounted such that it can direct shock waves or cleaning pulses of energy E at a wall 40 of a boiler vessel.

A plurality of tubes 42 are located in the boiler vessel and supported by wall 40. The cleaning pulses of energy E are also directed at the tubes 42. The wall 40 and tubes 42 tend to have soot or other buildup resulting from a combustion process in the boiler vessel that can cause losses in the overall system efficiency due to a reduction in the amount of heat that is actually transferred into a working fluid flowing through the tubes.

The impulse cleaning device 22 has a tubular body 60 that extends longitudinally with an open “horn” end 62 directed at the wall 40 and tubes 42 of a boiler vessel to be cleaned. The body 60 has an opposite closed head end 64 and air inlet ports 66 and a fuel inlet port 68. The body 60 defines a combustion chamber 80 that has a deflagration zone “a” and a detonation zone “b”. In the illustrated embodiment, the impulse cleaning device 22 is mounted to structure by at least one bracket 82 (FIG. 2) so the impulse cleaning device can be used to perform a cleaning operation of the boiler vessel.

The head end 64 of the impulse cleaning device 22 has its air inlet ports 66 connected to a source of air that can be provided under pressure through a valve 102 to deliver a flow of air P to the combustion chamber 80. This air source is used to fill and purge the combustion chamber 80, and also provides air to serve as an oxidizer for the combustion of the fuel. The inlet ports 66 may be connected to a facility air source such as an air compressor (not shown).

The fuel inlet port 68 is located at the head end 64 of the impulse cleaning device 22 and extends in a direction transversely relative to the air inlet ports 66. The fuel inlet port 68 is connected to a supply a flow of fuel F to the combustion chamber 80 through valve 104. The fuel F will be burned within the combustion chamber 80. The fuel F that is supplied to the combustion chamber 80 is mixed with the flow of air P.

The mixing of the fuel F and air P may be enhanced by the relative arrangement of air inlet ports 66 and the fuel inlet port 68. For example, a plurality fuel inlet ports 68 may be provided around the periphery of the combustion chamber 80. By placing the fuel inlet port or ports 68 at a location such that fuel F is injected into regions of high turbulence generated by the flow air P, the fuel and air may be more rapidly mixed to provide a more readily detonatable fuel/air mixture. As with the air inlet ports 66, the fuel inlet ports 68 may be disposed at a variety of axial and circumferential positions. The fuel inlet ports 68 may be aligned to extend in a purely radial direction, or may be canted axially or circumferentially with respect to the radial direction.

Fuel F is supplied to the fuel inlet ports 68 through the valve 104 that controls when fuel is allowed into the combustion chamber 80 of the impulse cleaning device 22. The valve 104 may be disposed within the fuel inlet port 68, or may be disposed upstream in a supply line that is connected to the fuel inlet port. The valve 104 may be a solenoid valve and may be controlled electronically by the controller 26 to open and close in order to regulate the flow of fuel F into the combustion chamber 80. The controller 26 may also electronically control the valve 102 and the flow of air P to the combustion chamber 80.

As illustrated in FIG. 1, an ignition device 120 is located near the head end 64 of the impulse cleaning device 22. In the illustrated embodiment, the ignition device 120 ignites the fuel/air mixture to create combustion C in the deflagration zone a. The ignition device 120 may take various forms. In particular, the ignition device 120 need not produce immediate detonation of the fuel/air mixture in every embodiment. However, the ignition device 120 provides sufficient energy for ignition that allows the combustion of the fuel/air mixture which can transition to a supersonic shock wave D, within the detonation zone b of the combustion chamber 80. The ignition device 120 may be connected to the controller 26 to operate the ignition device at desired or periodic times.

The controller 26 may be of any suitable type or combination of components to control the timing and operation of various systems, such as the valves 102, 104 and ignition device 120. As used herein, the term controller 26 is not limited to just those integrated circuits generally referred to in the art as a controller, but broadly refers to a master networked computer 128, processor, a microprocessor, a microcontroller, a programmable logic controller, an application specific integrated circuit, other programmable circuits suitable for such purposes and software or any suitable combination thereof.

The impulse cleaning device 22, constructed according to one aspect as illustrated in FIG. 1, includes the elongate body 60 defining the combustion chamber 80 that extends from the head end 64 to the horn end 62. Combustion of the fuel/air mixture takes place within the combustion chamber 80. In general, the combustion C will progress from the ignition device 120 through the mixture that is within the combustion chamber 80. FIG. 1 illustrates a cross-section of body 60 in the shape of a substantially round cylinder having a constant cross-sectional area. It will be apparent that other configurations of the body 60 and combustion chamber 80 are possible.

The body 60 may contain a number of obstacles (not shown) in the combustion chamber 80 disposed at various locations along the length of the body. The obstacles are used to enhance the combustion as it progresses along the length of the body 60, and to accelerate the combustion front C into a supersonic shock wave D before the combustion front reaches the horn end 62 at the downstream end of the body. The body 60 and obstacles may be fabricated using a variety of materials suitable for withstanding the temperatures and pressures associated with the repeated detonations. Such materials include but are not limited to: Inconel, stainless steel, aluminum and carbon steel.

The horn end 62 is formed as a diverging chamber that is connected directly to the body 60 of the impulse cleaning device 22. It will be apparent that although the diverging chamber need not be in direct contact with the impulse cleaning device 22, it is desirable that the combustion chamber 80 of the impulse cleaning device is in fluid flow communication with the diverging chamber of the horn end 62. The inner surface of the combustion chamber 80 is smooth and substantially circular in cross-section normal to the longitudinal central axis of the combustion chamber. It will be apparent hat other cross sectional shapes are also possible, as well as other axial profiles for the diverging chamber. Obstacles may also be placed in the flow, which can create alternate cross section profiles.

The cleaning system 20 incorporating the impulse cleaning device 22 uses supersonic shock waves D that form cleaning energy E to loosen accumulated debris, deposits and coatings that can accumulate on the walls 40 and tubes 42 of a boiler vessel or other device. High pressure fluid flow that follows the detonation helps blow the loosened material away from the cleaned surfaces. In operation, the impulse cleaning device 22 creates a supersonic shock wave D and its associated high-pressure flow from a combustion cycle, which is preferably repeated at high frequency. The impulse cleaning devices 22 can operate at frequencies of less than 1 Hz up to 100 Hz. Each combustion cycle generally includes a fill phase, an ignition event, a flame acceleration into detonation or supersonic phase, and a blowdown phase.

A single occurrence of a fuel fill phase, a combustion ignition, an acceleration of the flame front to supersonic, and the blow down and purge of the combustion products will be referred to as “a combustion cycle” or “a detonation cycle”. The portion of time that the impulse cleaning system 20 is active is referred to as “cleaning operation”. Time when the vessel to be cleaned is being actively used for its purpose will be referred to as “boiler operation”. As noted above, the parts to be cleaned need not be part of a boiler vessel; however, for simplicity of reference, the term “boiler operation” will be used to refer to the operation of any device being cleaned by the cleaning system 20.

One advantage of the cleaning system 20 is that, unlike other cleaning Systems, there is no need to shut down the boiler vessel or other parts being cleaned in order to operate the cleaning system. Specifically, it is possible for the cleaning operation to take place during the boiler operation. The cleaning system 20 need not be run continuously during the boiler operation. However, by providing the flexibility to operate the cleaning system on a regular cycle during boiler operation, an overall higher level of cleanliness can be maintained without significant downtime in boiler operation.

In the fill phase of the detonation cycle, air P and fuel F are fed into the impulse cleaning device 22. As shown in FIG. 1 and discussed above, pressurized air flow P is introduced into the combustion chamber 80 through the air inlet ports 66 and fuel F through the fuel inlet port 68. The fuel F and air flow P will mix to form a fuel/air mixture suitable for combustion within the impulse cleaning device 22. As more fuel and air are introduced and mixed, the combustion chamber 80 will tend to fill with the fuel/air mixture, starting near the closed head end 64 and proceeding along the length of the combustion chamber 80 as more fuel and air are introduced. Air flow P can be continuously fed to the impulse cleaning device 22 through the air inlet ports 66 during cleaner operation.

It may be desirable to use the valve 104 to control the introduction of fuel F into the impulse cleaning device 22 by means of the controller 26. It may also be desirable to control the air flow P for times when the cleaning system 20 is not operating. According to one aspect of the invention, the controller 26 can track the amount of time that has passed since the opening of a fuel valve 104. Based upon the rate of air input to the impulse cleaning device 22, the controller 26 can close the fuel valve 104 once a sufficient amount of fuel F has been added that the fuel/air mixture has filled the desired portion of the combustion chamber 80. The controller 26 then provides activation or ignition energy to the ignition device 120.

The ignition device 120 is controlled to initiate the combustion of the fuel/air mixture within the combustion chamber 80. If, for example, a spark initiator is used as the ignition device 120, the controller 26 sends electrical current to the spark initiator to create a spark at a predetermined time. In general, the ignition device 120 delivers sufficient energy into the mixture near the ignition device to form an expanding combustion front C in the fuel/air mixture. As this combustion front C consumes the fuel by burning it with the oxidizer present in the mixture, the combustion flame will propagate through the mixture within the combustion chamber 80.

As the combustion front C propagates through the combustion chamber 80 of the impulse cleaning device 22, the combustion front will reach the walls of the body 60 and any obstacles that are disposed within the combustion chamber. The interaction of the combustion front C with the walls of the body 60 and the obstacles will tend to generate an increase in pressure and temperature within the combustion chamber 80. Such increased pressure and temperature tend to increase the speed at which the combustion front C propagates through the combustion chamber 80 and the rate at which energy is released from the fuel/air mixture by the combustion front. This acceleration continues until the combustion speed raises above that expected from an ordinary deflagration process in the deflagration zone a to a speed that characterizes a quasi-detonation or detonation in the detonation zone b. This deflagration to detonation process desirably takes place rapidly (in order to sustain a high cyclic rate of operation), and so the obstacles are used to decrease the run-up time and distance that is required for each initiated flame to transition into a detonation.

The detonation or supersonic shock wave D travels down the length of the body 60 and out of the horn end 62 as cleaning energy E. From the horn end 62, the cleaning energy E may be directed at the object to be cleaned, such as the wall 40 and tubes 42. High pressure combustion products follow the supersonic shock wave D and flow through the horn end 62.

As the high-pressure products blow out of the impulse cleaning device 22, the continued supply of air flow P through the air inlet ports 66 will tend to push the combustion products downstream and out of the horn end 62. Such continued supply of air flow P is used to purge the combustion products from the body 60 of the impulse cleaning device 22. Once the combustion products are purged, the valve 104 for the fuel port 68 is opened, and a new fill phase may be started to begin the next combustion cycle.

The impulse cleaning device 22 can be controlled by the controller 26 to produce multiple supersonic shock waves D in rapid succession. The supersonic shock wave D that exits from the horn end 62 includes an abrupt pressure increase, as cleaning energy E, that will impact the parts of the object to be cleaned such as the wall 40 and tubes 42 of the boiler vessel. This cleaning energy E has several beneficial effects by breaking up accumulated debris and slag from the wall 40 and tubes 42 of the boiler vessel.

In one aspect, the cleaning energy E can produce pressure waves that travel through the accumulated slag and debris. Such pressure waves can produce flexing and compression within the accumulations that can enhance crack formation within the debris and break portions of the debris away from the rest of the accumulation, or from the wall 40 and tubes 42 of the boiler vessel. This is often seen as “dust” that is liberated from the surface of the accumulated stag.

In addition, the pressure change associated with the passage of the cleaning energy E can produce flex in the walls of the boiler itself, which can also assist in separating the slag from the wall 40 and tubes 42 of the boiler vessel. The repeated impacts from the cleaning energy E of repeating combustion cycles may excite resonances within the slag that can further enhance the internal stresses experienced and promote the mechanical breakdown of the debris. The repeated action of shock and purge is used to erode build-up that accumulates upon the wall 40 and tubes 42 of the boiler vessel.

It is important that the impulse cleaning system 20 be properly operating during boiler operation. The impulse cleaning device 22 may be located in an area that is either visually or audibly inaccessible by an operator or attendant so that verifying operation of the impulse cleaning device is not possible.

In one aspect of the invention the sensor 24 is mounted externally to the impulse cleaning device 22 in order to provide operational feedback to a control system or operator/attendant of a cleaning system 20. The sensor 24 can detect if a detonation or supersonic shock wave D occurred and can also provide information that can be monitored to establish if any decline in performance or loss of energy of the impulse cleaning device 22. This information can be used to perform diagnostics on the impulse cleaning device 22, to provide feedback for an emergency cutoff circuit, or to verify operation of the impulse cleaning device when it is located remotely relative to an operator/attendant or otherwise not readily accessible to a person.

The sensor 24 may be a strain gage, an accelerometer, an acoustic detection device, a pressure gage and an ion probe. According to one aspect of the invention as illustrated in FIG. 2, a strain gage 140 is located outside the impulse cleaning device 22 to provide the feedback information or detect an event, such as the occurrence of a detonation wave D in the impulse cleaning device. By mounting the sensor 24 externally of the combustion chamber, the hot and acidic gases from the combustion process do not contact the sensor and cause early degradation of the sensor and prolong its life.

The strain gage 140 of the sensor 24 is attached directly to a bracket 82 that mounts the body 60 relative to the boiler vessel. The stain gage 140 is oriented on the bracket so that it extends in a direction substantially parallel to the longitudinal central axis of the body 60. The strain gage 140 is electrically connected to the controller 26. The strain gage 140 detects thrust forces in the bracket that are indicative of a detonation event occurring in the combustion chamber 80. The thrust forces are also indicative of the displacement of the body 60 of the impulse cleaning device 22.

The strain gage 140 can be selected and calibrated to provide an information signal to the controller 26 that a detonation event has taken place and the intensity of the supersonic shock wave D. The controller 26 can be programmed to generate an alarm signal that activates an audible or visual signal on alarm 142 in response to a predetermined period of time elapsing before a detonation wave in the impulse cleaning device is detected by the sensor 24. The lack of a combustion event when expected can also trigger this alarm. The alarm signal can also be used to signal an alarm on the master computer 128.

The sensor 24 can also generate a signal as a function of the supersonic shock wave D in the impulse cleaning device 22, such as intensity. The controller 26 can use this information to control the delivery of fuel F to the combustion chamber 80, the delivery of pressurized air flow P to the combustion chamber and/or the delivery of ignition energy to the ignition device 120. Thus, the controller 26 receives the signal generated by the sensor 24 to control production of the supersonic shock wave D in response to the signal. This allows automatic feedback to the controller 26 as to whether impulse cleaning device 22 is operating correctly, or not at all, or if there is any degradation/improvement in performance. The sensor 24 and controller 26 provides accurate and quick time response feedback to the operator/attendant as to what the status of the impulse cleaning device 22 is and whether it is operating properly without requiring periodic inspection of the impulse cleaning device.

The sensor 24 may also be in the form of an accelerometer that can be selected and calibrated to provide an information signal to the controller 26 that a detonation event has taken place and the intensity of the supersonic shock wave D. The accelerometer sensor 24 would also be located outside the impulse cleaning device 22 to provide the feedback information or detect an event, such as the occurrence of a detonation wave D in the impulse cleaning device. By mounting the accelerometer sensor 24 externally of the combustion chamber, the hot and acidic gases from the combustion process do not contact the accelerometer sensor and cause early degradation of the accelerometer sensor and prolong its life.

The accelerometer sensor 24 could be attached directly to the bracket 82 or the body 60. The accelerometer sensor 24 would be mounted so that one of its axes extends in a direction substantially parallel to the longitudinal central axis of the body 60. The accelerometer sensor 24 would be electrically connected to the controller 26. The accelerometer sensor 24 detects acceleration of the component that it is attached to that is indicative of a detonation event occurring in the combustion chamber 80.

The controller 26 can be programmed to generate an alarm signal that activates an audible or visual signal on alarm 142 in response to a predetermined period of time elapsing before a supersonic shock wave D in the impulse cleaning device is detected by the accelerometer sensor 24. The lack of a combustion event when expected can also trigger this alarm. The alarm signal can also be used to signal an alarm on the master computer 128.

In another aspect of the invention illustrated in FIGS. 3 and 4, the sensor 24 is a robust sensor arrangement mounted to the impulse cleaning device 22. The sensor 24 can detect if a detonation event or supersonic shock wave D occurred in the combustion chamber 80 and can also provide information that can be monitored to establish if any decline in performance or loss of energy of the impulse cleaning device 22. This information can be used to perform diagnostics on the impulse cleaning device 22, to provide feedback for an emergency cutoff circuit, or to verify operation of the impulse cleaning device when it is located remotely relative to an operator/attendant or not readily accessible to a person. By using a robust sensor 24 that can withstand the hot and acidic gases from the combustion process, degradation of the sensor is avoided and it can provide a relatively long service life.

According to this aspect of the invention, the sensor 24 includes a pair of ion probes 160, as illustrated in FIGS. 3 and 4. The ion probes 160 are mounted so that a portion of each ion probe extends through the wall of the combustion chamber 80. The controller 26 provides a voltage bias across a gap in a portion of each of the ion probes 160 located in communication with the combustion chamber 80. When a combustion event occurs, the ions that are present in the gap of each ion probe 160 allow current to flow. The current varies based on amount of ions present in each gap.

Voltage across the gap of each ion probe 160 is monitored as the output signal. A spike in voltage is detected as the combustion event passes each ion probe 160. The ion probes 160 are located a predetermined distance d apart along the detonation zone b of the body 60. The velocity of the combustion wave front can be calculated across this predetermined distance d. The velocity determines if it is a combustion front C or supersonic shock wave D. The ion probes 160, thus, detect an event, such as the occurrence of a supersonic shock wave D in the impulse cleaning device 22 and provide feedback information about the combustion event in the combustion chamber 80.

The ion probes 160 can be selected and calibrated to provide an information signal to the controller 26 that a detonation event or supersonic shock wave D has passed the sensor 24 and the intensity of the combustion event. The controller 26 can be programmed to generate an alarm signal that activates an audible or visual signal on alarm 162 in response to a predetermined period of time elapsing before a supersonic shock wave D in the impulse cleaning device 22 is detected by the sensor 24. The alarm signal can also be used to signal an alarm on the master computer 128.

Another aspect of the invention concept uses a single ion probe 160 located a known distance from the ignition device 120. A spike in voltage is detected as the combustion event passes the ion probe 160. The average velocity of the combustion event can be calculated across this known distance. The average velocity determines if it is a combustion front C or supersonic shock wave D. The ion probe 160, thus, detects an event, such as the occurrence of a supersonic shock wave D in the impulse cleaning device 22 and provides feedback information about the combustion event in the combustion chamber 80.

The sensor 24 may be used to detect any or all of the following: the occurrence of a detonation or supersonic shock wave event; the intensity level (such as soft through loud); and the frequency content of the event (such as thud through ping). The signal information from the sensor 24 may be monitored or processed for multiple uses integral to aspects of the invention. Such uses include, but are not limited to, confirming that a detonation occurred; identifying a change in performance or loss of energy of the impulse cleaning device 22; providing feedback to the system 20 which enables adjustment of detonation parameters (such as: fuel/air ratios, fuel flow, air flow, charge/spark setup, and/or fill times) for optimal performance; facilitating diagnostics on the impulse cleaning device 22; providing feedback for an emergency cutoff circuit; or verifying operation of the impulse cleaning device when it is located remotely relative to an operator/attendant or otherwise not readily accessible to a person.

The output of sensor 24 may be sent directly, without anti-alias filtering, to an analog-to-digital converter for multiple uses, such as: detecting the occurrence of the event; providing minimal delay to identify the start of detonation; determining the intensity level of the event; and to a lesser degree, frequency content of the event. The output of the sensor 24 may be conditioned (filtered, amplified, etc.). The signal can have for multiple uses, such as: detecting the occurrence of the detonation event; providing identification of the start of detonation; determining the intensity level of the event; frequency content of the event, and detection of out-of-band frequency input.

Conditioning of the signal of the sensor 24 can be done in analog and/or digital form. The desired frequency band(s) and amplitude of the signal can then be processed for making operational decisions on the detonation parameters and/or notifications to the operator that may be needed. The signal conditioning provides a means to preserve signal to noise ratio in high-noise applications and/or to prepare the signal of the sensor 24 for use with following stages or process steps. Conditioning the signal by scaling and band-limiting for anti-aliasing purposes when interfacing to analog-to-digital converters (ADC) is one example. Another example is to filter (high, low or band) the signal to remove non-desired frequency content, improving the ability of the controller 26 to make operation decisions and/or notifications.

In one aspect of the invention, when high ambient noise exists, the use of a sensor 24 with an integrated gain stage (localized near the sensor) allows the signal to be sent to a remote location away from the impulse cleaning device 22 while preserving the signal to noise ratio. The sensor 24 may or may not require this feature, depending on the particular application and setup.

Using the signal of the sensor 24, one or multiple thresholds may be set to signify a particular event has occurred. For example, a low threshold may identify that “no detonation has occurred”, a mid-level threshold may identify that “a weakened detonation has occurred”, and third high-level threshold may identify that “a good detonation has occurred”. The use of at least one threshold is required to enable proper operation of the impulse cleaning device 22, while the other thresholds may provide additional capability of the impulse cleaning device that is useful to the operation of the impulse cleaning device. The use of “intensity level” threshold(s) can involve the use of an ADC and logic/processor device or simply an analog comparator.

“Windowing” the event in time with a start point and an end point, using the scheduled start determined by the controller 26, allows a counter to be used with a threshold circuit to enhance proper detection of a detonation event, as opposed to spurious noise. For example, a signal may need two out of five samples, or fifty out of a hundred samples, to be called a “good detonation”. The actual percentage of samples can be adjusted above or below the examples noted for a particular application and sensor configuration. Noisy environments may require a higher count to be achieved before declaring a “good detonation”. A higher capability signal processing device may use more samples to further extend operation into a noisy environment or provide better resolution information on the detonation event. Measuring the duration of the signal of the sensor 24 that meets a particular threshold or total count from a start point is another “windowing” implementation. Each of these windowing applications, and in combination, allow the controller 26 to provide detonation parameter modification and operator notification when necessary.

Selection of a particular frequency response of the signal of sensor 24 can indicate a “good detonation”. A high frequency “ping” may indicate a non-optimal detonation in which the fuel/air ratio or flow, charge/spark, and/or fill time may be adjusted to improve performance. For example, a detonation with relatively high frequency content may cause the impulse cleaning system 20 to increase the fill time. Conversely, a low frequency response may also indicate a non-optimal detonation, but cause the system to decrease the fill time. Fill time is but one example. Adjustment of the other detonation parameters can be made using the same frequency response information.

Characterization of a particular installation or setup using intensity and/or frequency response detected by the sensor 24 enables enhanced operation of the impulse cleaning device 22. For example, if a frequency response exists with relatively clean (minimal spurious and out-of-band) content and then later during operation, the signal begins to contain spurious or out-of-band signals, the system can flag a warning to the operator of a problem at that installation site. Thresholds or upper or lower frequency limits enable “good detonation” decisions to be made by the system. For example, an installation may have detonations that produce “main” frequencies from 15 Hz to 250 Hz and ones from 2 kHz to 4 kHz. These can be stored and/or analyzed for any shift in or absence of content allowing the system to adjust the detonation parameters to restore “good detonation” operation. The “main” frequencies used to make the determination may be multiple bands, single bands, or simply a single frequency.

An order of “modifying decisions” may be designed such that: adjustment of the fill time to a particular point, then fuel/air ratio may be adjusted to a prescribed limit, then total flow of fuel or air may be modified. The system 20 can then optimize performance without outside intervention, and if necessary, notify an operator that maintenance will be needed. The above is but one example. Adjustment of the other detonation parameters in various orders can be made for a particular installation or system setup along with notifications when particular thresholds or limits are reached. Thresholds set and/or trending data collected on signal content can allow health and maintenance prediction for installations, reducing the need for scheduled maintenance which could be unnecessary.

To provide a check on the condition of the sensor 24, during a period before or after a detonation event, a sensor “quiescent” value can be tested. If it exceeds a threshold, a decision can be made that the environment is “too noisy” or the sensor 24 is faulty, enabling a maintenance notification to be sent to an operator and/or a system protection function to be activated (such as disabling operation of the cleaning device, fuel valves, spark, etc.).

It will be appreciated that such an impulse cleaning system 20 is not limited to industrial boilers, but may be used to provide cleaning on a variety of different surfaces which may experience fouling or accumulation of debris. Examples of vessels having surfaces which may be cleaned using the systems and techniques described herein include but are not limited to: vessels used in cement production, waste-to-energy plants, and coal-fired energy facilities, as well as reactors in coal gasification plants.

The various embodiments of cleaning systems described above thus provide a way to achieve soot or ash removal from the wall 40 and tubes 42 of the boiler vessel. These techniques and systems also allow for periodic operation without the need to shut down the device being cleaned for extended periods of time.

Although the systems herein have been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the systems and techniques herein and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow. 

1. A system for removing accumulated debris from a surface of a vessel, the system comprising: a vessel having a surface to be cleaned; a impulse cleaning device defining a combustion chamber in which combustible fuel and air are mixed and ignited to produce supersonic combustion that is directed at the surface to be cleaned within the vessel; and a sensor associated with the impulse cleaning device, the sensor for detecting a condition within the impulse cleaning device and generating a signal in response to a detected condition.
 2. The system of claim 1 wherein the sensor detects a supersonic combustion event in the impulse cleaning device.
 3. The system of claim 2 further including an apparatus that generates an alarm signal in response to a predetermined period of time elapsing before supersonic combustion in the impulse cleaning device is detected by the sensor.
 4. The system of claim 1 wherein the sensor generates a signal as a function of the combustion in the impulse cleaning device.
 5. The system of claim 1 further including a controller for receiving the signal generated by the sensor to control production of combustion in response to the signal.
 6. The system of claim 5 in which the controller controls production of combustion by controlling at least one of the delivery of combustible fuel to the combustion chamber, the delivery of air to the combustion chamber and the delivery of ignition energy to the combustion chamber.
 7. The system of claim 1 wherein the sensor is selected from the group comprising a strain gage, an accelerometer, an acoustic detection device, a pressure gage and an ion probe.
 8. The system of claim 7 wherein the sensor is a strain gage mounted outside of the combustion chamber of the impulse cleaning device to sense displacement of the impulse cleaning device.
 9. The system of claim 7 wherein the sensor is an accelerometer mounted outside of the combustion chamber of the impulse cleaning device to sense acceleration of a component of the impulse cleaning device.
 10. The system of claim 7 wherein the sensor comprises an ion probe spaced from a know location a predetermined distance along the impulse cleaning device, the ion probe being in communication with the combustion chamber and being capable of detecting the movement of a combustion event past the ion probe.
 11. A cleaner for removing accumulated debris from a surface of a vessel, the cleaner comprising: a impulse cleaning device defining a combustion chamber in which combustible fuel and air are mixed and ignited to produce combustion that results in a shock wave directed at the surface to be cleaned within the vessel; and a sensor operably connected with the impulse cleaning device, the sensor detecting a condition of the impulse cleaning device and generating a signal in response to a detected condition.
 12. The cleaner of claim 11 wherein the sensor detects supersonic combustion in the impulse cleaning device.
 13. The cleaner of claim 2 further including an apparatus that generates an alarm signal in response to a predetermined period of time elapsing before supersonic combustion in the impulse cleaning device is detected by the sensor.
 14. The cleaner of claim 11 wherein the sensor generates a signal as a function of the combustion in the impulse cleaning device.
 15. The cleaner of claim 14 wherein the sensor generates a signal having frequency information to determine the quality of the combustion as a function of a change in the frequency information.
 16. The cleaner of claim 15 further including a controller to adjust detonation parameters based on the sensor signal frequency information.
 17. The cleaner of claim 14 wherein the sensor generates signal intensity level information to determine the quality of the combustion as a function of a change in intensity level.
 18. The cleaner of claim 17 further including a controller to adjust detonation parameters based on the sensor signal intensity level information.
 19. The cleaner of claim 14 further including a windowed counter to determine the quality of the combustion event by establishing the duration of combustion
 20. The cleaner of claim 14 further including a sensor having a local integrated gain stage to enhance the transmission of the signal from the sensor to the controller.
 21. The cleaner of claim 11 further including a controller for receiving the signal generated by the sensor to control production of combustion in response to the signal.
 22. The cleaner of claim 21 in which the controller controls production of combustion by controlling at least one of the delivery of combustible fuel to the combustion chamber, the delivery of air to the combustion chamber and the delivery of ignition energy to the combustion chamber.
 23. The cleaner of claim 11 wherein the sensor is selected from the group comprising a strain gage, an accelerometer, an acoustic detection device, a pressure gage and an ion probe.
 24. A method for removing accumulated debris from a surface within a vessel, the method comprising: providing a impulse cleaning device defining a combustion chamber; delivering a flow of air to the combustion chamber; delivering a flow of combustible fuel into the flow of air in the combustion chamber; mixing the combustible fuel and air within the combustion chamber; periodically igniting the fuel and air mixture to produce supersonic combustion; directing the supersonic combustion into the vessel at a surface to be cleaned to loosen and remove accumulated debris from the surface of the vessel; and sensing the supersonic combustion in the impulse cleaning device and generating a signal in response to sensing the supersonic combustion.
 25. The method of claim 24 further including the step of generating an alarm signal in response to a predetermined period of time elapsing before supersonic combustion in the impulse cleaning device is sensed.
 26. The method of claim 24 further including the step of controlling production of combustion as a function of the signal generated in the sensing step by controlling at least one of the delivery of combustible fuel to the combustion chamber, the delivery of air to the combustion chamber and the delivery of ignition energy to the fuel and air mixture in the combustion chamber. 